1. Field of the Invention
The present invention relates to a gas removal filter, and more particularly to an apparatus for and a method of estimating the ion exchange group consumption ratio of an ion exchanger for use in gas adsorption applications.
2. Description of the Related Art
Heretofore, the service life of an ionic gas adsorption filter has been managed by any one of the following processes:
(1) The total amount of a gas adsorbed by the filter is periodically integrated from the concentration of the gas on the inlet side of the filter and the rate of air flowing through the filter, and then compared with a known absorption limitation for judging the service life of the filter.
(2) The concentration of the gas on the inlet side of the filter and the concentration of the gas on the outlet side of the filter are periodically measured to confirm a reduction in the gas removal capability of the filter.
(3) It is confirmed whether or not the concentration of the gas on the outlet side of the filter is of a management value or lower.
The concentration of a gas is generally measured by an analyzer such as an ion chromatograph, a monitor for detecting a pH change, or a glass tube (detecting tube) filled with a detecting agent. While all the above processes for managing the service life of a gas removal filter are based on the measurement of the concentration of a gas, if the concentration of a gas to be measured is lower than 10 xcexcg/m3, then the measurement needs to rely on an analyzer which is capable of analyzing a trace amount of gas. However, such an analyzer is expensive and requires an operator who is knowledgeable in analytic processes for its operation though the analyzer is characterized by high analyzing accuracy.
It is therefore an object of the present invention to provide a gas removal filter which is capable of detecting the ion exchange group consumption ratio of an ion exchanger without a short period of time and easily detecting a remaining adsorption capability without the need for measuring a gas concentration.
A gas removal filter according to the present invention has an ion exchanger for adsorbing a gas and at least a pair of electric resistance measuring electrodes disposed on the ion exchanger.
By measuring a change in the electric resistance between at least the pair of electric resistance measuring electrodes disposed on the ion exchanger, it is possible to estimate an ion exchange group comsumption ratio of the ion exchanger. The ion exchange group consumption ratio of the ion exchanger can be detected in a short period of time, and a remaining adsorption capablility of the ion exchanger can be known with ease.
A removal method according to the present invention comprises the steps of placing at least a pair of electrodes on a gas removal filter having an ion exchanger for measuring the electric resistance of the ion exchanger, measuring the electric resistance between the electrodes with electric resistance measuring means, and estimating an ion exchange group consumption ratio of the ion exchanger from a change in the electric resistance to manage a consumed quantity of an ion exchange group.
With the above method, it is possible to manage the service life of the gas removal filter easily withing a short period of time without the need for a gas analyzer for analyzing a trace amount of gas, such as an ion chromatograph, a gas chromatograph or the like. Thus, the cleanness of a clean room or the like can be managed with ease.
In the method of using a gas removal filter according to the present invention, it is preferable to adjust the humidity around the ion exchanger when the electric resistance of the ion exchanger is to be measured. Particularly when the humidity around the ion exchanger is adjusted to be low, the ion exchanger is not affected by moisture, and hence the ion exchange group consumption ratio of the ion exchanger can be estimated accurately.
The above and other objects, features, and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.